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When you list a domain in WMT you get access to the stats from the subdomain, but if someone else verifies the subdomain then WMT no longer gives you access to the subdomain stats. Now there was no mention that this is the case with domain authority but it is my guess it is. Some sites that had users content of low quality suffered from the panda update, Matt Cutts suggested moving user content to subdomains to separate content. It is my belief that sites that give other users a subdomain as bandcamp.com do do not share domain authority because users list their subdomain in WMT and analytics and stuff. But on your own site you will get domain authority from one to the other. So in short I would move to your own domain, I don’t think you would be getting anything from bandcamp ,and I think you will from your own domain.